One who trusts lightly will be harmed, and one who sins against his own soul will suffer even worse harm.^[1] Note that this statement does not contradict that of the apostle, who says regarding charity, It bears all, believes all, hopes all. Charity will never end,^[2] since here the perfection of a good will is present, always ready for any good work. The other statement, rather, describes levity of soul, always changeable and lacking in stability. For this reason it is written elsewhere, The fool changes like the moon.^[3] One, therefore, who with itching ears lets himself be easily convinced, stops listening to the truth and turns to fables will suffer harm in both his intelligence and his virtue, and one who harms his own soul will be considered a fool.

Like an arrow stuck in a dog’s leg are words in the heart of a fool.^[1] The dog is at times explained in a good sense, at times in a bad. The good sense one finds in the Psalter: They return at evening, hungry as dogs, and roam about the city,^[2] which indicates the doctors of Judaism who hunger for the justice of God’s law.^[3] After the evening of Christ’s passion, they went diligently about the city of the church, defending it with the barking of their preaching. We also read in the Gospel that the dogs licked the wounds of Lazarus the beggar.^[4] The dog is understood in a negative sense, however, when it indicates the filthiness of sinners, as in this passage: As the dog returns to its vomit, so the fool repeats his folly.^[5] The arrow sticks in the dog’s thigh when, under the devil’s inspiration, perverse concupiscence lodges in the heart of a sinner. He is rightly called foolish, since like an ox he is led to the slaughter, neither thinking of himself nor keeping himself from ruin and eternal death.